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Reviewer: H. Van Dyke Parunak

One of the most popular forms of agent technology is that of programs whose execution can be interrupted on one processor and resumed on another. The authors provide a practitioners' introduction to these programs. Part 1 briefly describes the Internet's potential for conveying running programs as well as static data, outlines potential applications of this technology, and introduces some basic concepts to unify the discussion of individual systems in the remainder of the book. Part 2 covers three systems that do not use Java, and Part 3 covers one system that does. Each of the systems covered is described in a chapter written jointly by the authors of the book and one or more of the developers of that system. The enclosed CD-ROM includes each of the systems, ready for installation on a Unix system. Part 2 offers descriptions of Telescript, written with James White; Agent Tcl, with Robert Gray; and Agents for Remote Access (ARA), with Holger Peine. Part 3 is dedicated to the Aglets system, and was written with the Aglets Workbench team. Java is the language most often associated with mobile agents, and most new systems use it as their foundation. However, the non-Java systems discussed by the authors are more mature and offer more extensive examples of the kinds of agent capabilities that are useful in mobile applications. Software engineers who want to respond to the growing demand for expertise in mobile agents need the kind of help that this book promises. However, this particular volume is less effective than one might desire, for three reasons. First, the field has changed since the authors completed their manuscript. Of the four systems described, only two, Telescript and Aglets, are commercially supported, and thus viable candidates for widespread deployment in commercial applications. General Magic has abandoned Telescript for its new Java-based product, Odyssey. Also, much of the vision for Aglets was due to Danny Lange, who is now part of the Odyssey team. Thus, both of the commercial packages discussed have been bypassed by more recent technology: not only Odyssey, but Concordia, Voyager, Cybele, and Agent Development Environment. A system developer trying to select a platform for mobile agents today will almost certainly prefer information on these platforms. Second, the coverage is uneven. The book devotes 21 pages to Telescript, 38 to Agent Tcl, 79 to ARA, and 128 to Aglets. In spite of their differences in length, the chapters describing the first three systems are similar in tone. They offer systematic expositions of the underlying architecture and key concepts of each system, and work through example applications. The Aglets material lacks the systematic exposition of the architecture. It occupies three chapters. The first guides the reader in installing the Aglets system from the CD-ROM and bringing up a demonstration application. The second lists the Aglets classes and supporting methods, exceptions, and variables. The third is an index of all Aglets fields and methods. While the latter two Aglets chapters are useful, they are very different in kind and level of detail from the information provided about the other systems. Third, the CD-ROM is an excellent idea whose execution is flawed. It contains the complete text of the book in HTML form, and distributions of all four systems described (all for Unix, plus a distribution of Aglets for 32-bit Windows systems). The book promises that the CD-ROM also contains “references to other agent systems which have been developed, agent resources on the Internet, and tips on obtaining software updates that are developed for the included agent systems.” All of these are necessary accompaniments to a book on such a rapidly changing field; unfortunately, none of them is included on the CD-ROM in the review copy. The book also promises that the publisher's Web site will contain URLs for updated software and examples, but to date it does not. The book includes a glossary of more than 50 technical terms related to mobile agents; a bibliography of over 90 items, some published in 1997; and a brief index. While the systems it describes are not the most current candidates for broad commercial deployment, its analysis of them provides a readable introduction to the techniques of mobile agents and the applications for which they may be useful.